It is common in the heat treat furnace art to equip a heat treat furnace with an integral quench. The quench is a quench tank situated beneath the furnace and contains a liquid quench medium. The quench medium is typically a liquid salt, water or oil bath into which the heated work is placed for rapid cooling to meet time-temperature heat treat process requirements. The heat from the work is given off to the liquid in the quench tank. Some type of heat sink has to be provided in the tank to return or maintain the liquid bath at its ambient temperature. This is typically accomplished by placing coils containing coolant within the bath. The coolant within the coils receives heat from the liquid in the quench tank and then passes through a heat exchanger located outside of the quench tank where the coolant is cooled before returning to the inlet end of the coils in the quench tank. This is an effective and efficient cooler. It is somewhat expensive because of the cost of the heat exchanger necessary for the cooling arrangement to function as a closed loop. Also, the cooling coils are directly exposed to the quenchant. Should the coils develop a leak (which can happen on the basis of thermal expansion-contraction considerations) the cooling gas can leak directly into the quenchant. It is also possible, in the prior art closed loop system, for the coolant gas to pick up oil or hydrocarbons from the fan compressor and some hydrocarbons could conceivably leak into the quenchant vis-a-vis the coil portions within the tank. The quench tank is sealed and should the quenchant be water, steam is given off which can react with oil or hydrocarbons to produce an explosion.
In any gas heat exchanger, there is a need to produce a simple, inexpensive but efficient seal which is able to withstand the thermal stresses imposed on the heat exchange by the changing thermal stress gradients caused by the hot and cold gases within the heat exchanger. There are far too many heat exchanger designs in the heat treat field to discuss prior art seal arrangement in this background section. One type of seal arrangement that can be generally described uses a spring biased seal to maintain the hot heat exchanger components against the cold heat exchanger part where the two components generally meet i.e., the manifold and return duct. In time, any spring biasing seal will wear and leak. Still another seal arrangement uses a water jacket adjacent an elastomer seal which is an expensive construction.